Rounding Off Numbers

Rounding Off Numbers

What is Rounding Off?

Rounding off is a way of making numbers simpler by writing them as the number they are closer to.

Numbers can be rounded off in several ways:

To the nearest whole number.

For example, 5.8 to the nearest whole number is 6 – it lies between 5 and 6 but is closer to 6.

To the nearest ten.

For example, 543 to the nearest ten is 540 – it lies between 540 and 550 but is closer to 540.

To the nearest hundred.

For example, 1297 to the nearest hundred is 1300 – it lies between 1200 and 1300 but is closer to 1300.

To the nearest thousand.

For example, 2679 to the nearest thousand is 3000 – it lies between 2000 and 3000 but is closer to 3000.

To the nearest decimal place – this is covered in our ‘Decimals’ lesson.

The Golden Rules

When asked to round off a number here are the golden rules to follow:

Identify the digit you are being asked to round off based on place value e.g. the tens column, the hundreds column etc…

Look at the next digit in the number sitting to the right of the one you are rounding.

If it is a 5 or higher you round up.

If it is lower than a 5 you round down.

Rounding to the Nearest Whole Number

Rounding to the nearest whole number means we are going to round the units column.

Rounding to the nearest whole number requires a little knowledge of decimals because we will need to look at the tenths column in order to round the units up or down. If you don’t fully understand what the tenths column is you can quickly read the ‘What are Decimals?’ section of the ‘Decimals’ lesson.

When asked to round to the nearest whole number you follow the rounding off golden rules:

Find the digit you are being asked to round in the units column

Look at the digit to the right of the units column (this is the tenths column which sits to the right of the decimal point).

If it is a 5 or over round up.

If it is less than 5 round down.

Lets look at an example:

Example

Question: What is 2.7 rounded off to the nearest whole number?

We are being asked to round to the nearest whole number, this means the units columns:

2.7

So after identifying the correct column, we look at the digit to the right of it:

2.7

If the digit is 5 or over, we round up. In this case the digit is 7, so we round up. And our answer is:

3

Rounding to the Nearest Ten

To round to the nearest ten we must look at the digit in the tens column.

Next, look at the digit to the right of this in the units column.

If it is 5 or over round up.

If it is under 5 round down.

Example

Question: Round 152 to the nearest ten.

We are being asked to round to the nearest ten:

152

The digit to the right of the tens column is 2:

152

Because it is less than 5, we round down and our answer is:

150

Rounding to the Nearest Hundred

To round to the nearest hundred we must look at the digit in the hundreds column.

Next, look at the digit to the right of this in the tens column.

If it is 5 or over round up.

If it is under 5 round down.

Example

Question: Round 45178 to the nearest hundred.

To round 45178 to the nearest hundred we must look at the hundreds column: